# Effective Models of Quantum Gravity

Conference Date:
Friday, November 9, 2007 (All day) to Sunday, November 11, 2007 (All day)
Scientific Areas:
Quantum Gravity

Recent years have witnessed a growing popularity, in the quantum gravity community, of approaches which, rather than embarking in the formulation of a full theory of quantum gravity from first principles, try to gain some intuition on the problem studying what possible modifications of our standard theories of particles and fields might emerge approaching the Planck scale.  Such "effective models" might take inspiration from more ambitious quantum gravity frameworks (like e.g. the string-inspired non-commutative field theories) or simply try to relax or modify some fundamental requirements which appear natural in standard theoretical frameworks, are very well tested for energy scales probed by current experiments, but could lose their fundamental role when quantum and gravitational effects become important at Planckian regimes (see e.g. models with "twisted" or "quantum deformed" Poincare' symmetries or with a "locality bound").  Part of the large interest toward some of these models is motivated by the possibility that they might lead to experimentally observed predictions thus providing first examples of quantum gravity frameworks which can be challenged by reality.  Researchers in the community working on different topics seem to rarely have had a chance to compare and discuss their approaches and result.  The workshop intends to provide an opportunity for scientists who have been working on closely related topics but that often come from different backgrounds to meet, interact and have an opportunity to learn about recent advances in the different models.  A limited number of participants, mostly blackboard talks and plenty of time for discussions will encourage an intimate and informal atmosphere.

Florian Girelli, Sissa Trieste, Italy

Ted Jacobson, Maryland University

Jack Ng, North Caroline

Jorge Alfaro, Chile University, Catolica

Balachandran, Syracuse University

Jorge Pullin,  Louisiana State University

Jerzy Kowalski, Wroclaw University, Poland

Etera Livine, Lyon, France

Steven Giddings, UC Santa Barbara

Jerzy Lukierski, Wroclaw University, Poland

David Mattingly, UC Davis

Matt Visser, Victoria U, Wellington

Jorge Alfaro

Lorentz Invariance Violation in the Standard Model induced by Quantum Gravity

The most important problem of fundamental Physics is the quantization of the gravitational field. A main difficulty is the lack of available experimental tests that discriminate among the theories proposed to quantize gravity. Recently we showed that the Standard Model(SM) itself contains tiny Lorentz invariance violation(LIV) terms coming from QG. All terms depend on one arbitrary parameter $\alpha$ that set the scale of QG effects. We discuss several effects,including the Ultra High Energy Cosmic Rays GZK cutoff.

Giovanni Amelino-Camelia

Doubly Special Relativity: Myths, facts, and some key open issues

AP Balachandran

Quantum fields on the Moyal plane

Steve Giddings

High-energy gravitational scattering and locality

Florian Girelli

QG phenomenology and Finsler geometry

Finsler geometry is a natural generalization of Riemannian geometry.  I will describe various arguments (analog models, higher order derivatives field theories, symmetry deformation) favoring Finsler geometry as the natural framework to provide an effective description of semi-classical space-time.

Jerzy Kowalski-Glikman

DSR from quantum gravity

I will describe the steps of derivation of Doubly Special Relativity from no gravity limit'' of quantum gravity. Some of the steps are pretty well understood, and some are quite speculative. I will try to honestly point out which are which.

Markopoulou

Emergent locality in quantum gravity

John Moffat

Finite, non-local quantum gravity

Daniel Sudarsky

Quantum Gravity Phenomenology  without violations or modifications of  Lorentz Symmetry

Bill Unruh

Where do the particles come from?

Analog models of gravity server two purposes, one is giving us hints into ways in which we might be able to alter our theory of gravity, and another is using them to understand features of ordinary gravity. This talk will focus on the second, more conservative role of analogs. Black Hole evaporation is one of the most puzzling features of gravity and quantum theory. The derivation by Hawking is nonsense, in that it uses features of the theory in regimes where we know the theory is wrong.Analog models of gravity have given us a clue that despite the shaky derivation, the effect is almost certainly right. Where then are the particles in black hole evaporation really created? One of the most useful features of analog models is their maleability-- allowing us to change conditions in the model which are impossible to change in the true theory of gravity. In particular one can shift the location and  temperature of the horizon for the various incoming frequencies and ask which of the horizon temperatures determines the  temperature of the outgoing radiation. Also one can ask which of the velocities of the waves determines the location of the horizon and the concomitant temperature. This talks will examine these questions in the context of the simplest of analogs for a black hole. It may also look at some analytic work in support of the numerical results.

Luis Urrutia

Radiative corrections in the electrodynamics sector of the Myers Pospelov Model

Matt Visser

Can we hope to justify the Einstein equations in analogue/emergent spacetimes?

Analogue/ emergent spacetimes currently are useful fordescribing kinematic aspects of quantum gravity, that is: How doparticles and fields react to the presence of the analogue/ emergentspacetime? But obtaining suitable Einstein-like dynamics for theanalogue/ emergent spacetime is certainly much more difficult, andmay in most (hopefully not all) analogue models prove to beimpossible. Without providing any definitive solution to thisproblem, I will try to explore the possibilities and summarize thecurrent situation.

Silke Weinfurtner

Physical existence of signature change events and consequences of an absolute time in emergent spacetimes from Bose gas hydrodynamics.

We present an example of emergent spacetime as the hydrodynamic limit of a more fundamental microscopic theory. The low-energy, long-wavelength limit in our model is dominated by collective variables that generate an effective Lorentzian metric. This system naturally exhibits a microscopic mechanism allowing us to perform controlled signature change between Lorentzian and Riemannian geometries. We calculate the number of particles produced from a finite-duration Euclidean-signature event, where we take the position that to a good approximation the dynamics is dominated by the evolution of the linearized perturbations, as suggested by Calzetta and Hu [Phys. Rev. A 68 (2003) 043625]. We adapt the ideas presented by Dray et al. [Gen. Rel. Grav. 23 (1991) 967], such that the field and its canonical momentum are continuous at the signature-change event.  We investigate the interplay between the underlying microscopic structure and the emergent gravitational field, focussing on its impact on particle production in the ultraviolet regime. In general, this can be thought of as the combination of trans-Planckian physics and signature-change physics. Further we investigate the possibility of using the proposed signature change event as an amplifier for analogue "cosmological particle production" in condensed matter experiments.